It's been almost 50 years since the Supreme Court said you're wrong...Agents can also offer patentability opinions to their clients, of their clients' inventions and possibly also of others' inventions if reexamination is being sought.
Sorry, it's been a long day and a while since I last read Sperry (professional responsibility course in law school). Please point out how exactly I was wrong. I assumed talking with your client about the patentability of an application to be part of the drafting process, along with communicating with the PTO. How else would you draft an application? Reexamination falls under the purview of "communicate with the PTO".
Certainly, patent agents are licensed to conduct searches of the prior art and prepare reports when such a function is inherent to proper preparation of a patent application.
I guess I had to enumerate what I (and apparently you) considered inherent parts of the drafting process.
I guess I should list things agents cannot do:
1) give advice on the potential infringement of a patent;
2) draft any kind of contract (including filling in contracts for clients);
3) represent a client in court*;
4) be a partner in any firm in a state that follows the model rules of professional conduct (most states I know);
*Anticipating Robert KS's objection, I don't consider the board to be a court.
Sorry if I "colored" the scope of what an agent can do. I also don't think that the scope of what an agent can do is really that expansive. It's still pretty much limited to things required for the drafting of the application and drafting correspondences for the client to the PTO. My wife is a CPA and the scope of what a patent agent can do is pretty much on par with what a CPA can do when representing a client before the IRS.